Technical Abstract:
Channelized agricultural headwater streams are a common feature within agricultural watersheds of the Midwestern United States. These small streams have been impacted by the physical and chemical habitat alterations incurred to facilitate agricultural drainage. Quantitative information on the instream wood characteristics within channelized agricultural headwater streams is lacking and needed to assist with designing stream restoration projects for these small streams. We conducted a large scale assessment to determine if the presence and diversity of instream wood types differs among Scioto River Basin (Ohio) headwater streams exhibiting four channel types ranging from recently channelized to unchannnelized. Instream wood data collected from 118 headwater streams were obtained from the Ohio Environmental Protection Agency. We also conducted a small scale field study in twelve headwater streams within the Upper Big Walnut Creek watershed within the Scioto River basin to determine if the amounts and types of instream wood differ between channelized and unchannelized agricultural headwater streams. Our large scale assessment found the presence of rootwads, rootmats, and logs and the diversity of instream wood differed among channel types with unchannelized streams having the greatest values and recently channelized streams having the least values. Our small scale field study observed that the diversity of instream wood, density of instream wood, and density of large (i.e., > 1 m length and > 0.10 m diameter) log jams was greater in unchannelized than channelized streams. Channelized streams contained mostly small simple wood pieces, large simple wood pieces, and large overhanging vegetation. Unchannelized streams possessed mostly small simple wood pieces, large rootwads, and large log jams. Our results suggest that restoration designs for channelized agricultural headwater streams should use practices that increase the amount of instream wood and alter the proportion of different types of instream wood.